1. Field of the Invention
The present invention relates to a biodecomposable or biodisintegrable moldable material and a molded article produced therefrom. More particularly, the present invention relates to a biodecomposable or biodisintegrable moldable material wherein a natural high molecular weight substance such as starch or cellulose is incorporated with a specific proportion of a biodecomposable or biodisintegrable thermoplastic resin, and to a molded article produced therefrom.
2. Description of the Prior Art
As various synthetic resin (plastic) articles produced heretofore are devoid of any biodisintegrability, unlike natural high molecular weight substances such as cellulose, a serious problem is encountered in the treatment of waste plastic articles. For example, plastic bags made of polyvinyl chloride are not biodecomposable by the action of microorganisms. Accordingly, waste bags remain in the soil semi-permanently without undergoing any chemical decomposition. Further, movement toward prohibiting or limiting the use of plastic as packaging materials is being encouraged in recent years in Europe and America. Thus, this problem in the treatment of waste plastic articles now becomes one of urgent necessity on a global scale.
In the prior art, products heretofore developed and actually put into practice for solving problems in the treatment of waste plastics have been limited to articles in the form of a sheet or film wherein polyethylene is incorporated with 6-25% by weight of starch. However, such products are poor in starch content so that biodecomposition of starch by microorganisms is not completely attained. In addition, the products still maintain their structure and are not disintegrated into pieces even if the contained starch is completely biodecomposed. On the other hand, if the starch content is increased to overcome the above defect, the intended biodisintegration of the products will certainly take place but a plastic containing starch in a large amount is devoid of any plasticity so that the products, for example, in the form of a sheet are significantly inferior in mechanical properties and are hardly used for the manufacture of molded articles where a secondary processing treatment in required.
Thus, the known conventional biodisintegrable plastics are utterly unsatisfactory in the degree of biodisintegration itself or otherwise poor in mechanical properties and processability.
Under the above circumstances, there is a great demand for developing new type biodisintegrable plastic materials which enable good biodisintegration and prevent deterioration in mechanical properties and thermoformability by incorporation of natural high molecular weight substance with a specific plastic substance capable of being decomposed by microorganisms.